How to fix video issue after merging in ffmpeg?

Question

fmpeg

Aloha!
There are three videos that need to be glued into one using FFmpeg:

ffmpeg -i "concat:video2_op.ts|video2.ts|video2_ed.ts|" -c copy -bsf:a aac_adtstoasc video2_done.mp4

video2_op.ts and video2_ed.ts - generated video from picture, no sound, duration 5sec.
and everything would be fine, but the final video is completely without sound.
I was told that I need to add another 0.1 second video, cut off from video2.ts, at the very beginning:

ffmpeg -i "concat:1f_video2.ts|video2_op.ts|video2.ts|video2_ed.ts|" -c copy -bsf:a aac_adtstoasc video2_done.mp4

this solved the sound problem, but another one appeared - the video starts not from the very beginning, but from 6 seconds, i.e. skips just the passage that occupies video2_op.ts
help solve the problem.

Answer 1

the problem turned out to be that there was no audio track on video2_op.ts and video2_ed.ts